Andreas Auensen successfully defended his thesis "Prognostic factors and outcomes in patients with severe aortic stenosis referred for evaluation of possible surgical aortic valve replacement" in February 2018.

Narrow aortic valve, also known as aortic stenosis, is the most common valvular heart disease in the western world. It often leads to heart failure and reduced quality of life due to the constant narrowing of the aortic valve. Surgically replacing the valve is an efficient treatment against complications and premature death.

In his studies Dr. Auensen followed 442 patients who were treated at Oslo University Hospital for aortic valve replacement. 351 of them were referred to surgery and the rest were either refused surgery due to insufficient amount of symptoms, high risk or the patient declined surgery as an option.

A wide range of clinical outcomes were observed;
- 90% of the patients who underwent surgery were alive after three years
- Patient-reported quality of life was substantially better one year after surgical valve replacement
- The amount of strokes during the first year post-surgery warrants attention
- Regular blood tests taken at the first assessment may possibly indicate the risk of complications in the post-surgery period

Due to the extensive knowledge of the beneficial effect of surgery on survival, it is currently ethically impossible to conduct a study in which patients with severe aortic stenosis are randomized to either surgery or only follow-up.

In modern medicine, clinical observational studies will be very important as new treatment options develop further, today's treatment options for aortic stenosis being an example of this.